Method and apparatus for forming cylinders from strip material

ABSTRACT

A cylinder-forming method and apparatus is disclosed in which a pre-cut blank of strip material is positioned against a locating abutment and clamped within a rotatable mandrel. As the mandrel is rotated, first and second guide means form the blank to the periphery of the mandrel with flattened end portions being formed on the blank adjacent an end gap. Gripping means seize the blank before unclamping the mandrel, and thereafter transfer the formed blank with its gap in a known predetermined position into the jaws of an electric flash welder wherein the ends of the blank are joined by welding.

Patented May 16, 1972 3,662,940

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4 Sheets-Sheet METHOD AND APPARATUS FOR FORMING CYLINDERS FROM STRIP MATERIAL DESCRIPT ION OF THE INVENTION This invention relates to fonning pre-cut blanks of strip material, and in its principal aspect concerns a method and apparatus for fonning such a blank into a cylinder and transferring it to a welding apparatus with its end gap located in a precisely predetermined position for welding.

A principal object of the invention is to provide an improved method and apparatus for forming generally cylindrical shapes from pre-cut blanks of sheet material, producing a blank of uniform shape with an end gap positioned at a precise predetermined location relative to the forming apparatus.

A further object is to provide an apparatus in which the end gap of a formed blank may be simply and accurately positioned in the jaws of an electric flash welder for joining the ends of the blank by welding. It is intended that no complex mechanism be required to find the gap in the blank after the forming operation, with the blank being instead transferred directly from the forming apparatus to the welding apparatus with the gap in a correct predetermined position for welding at all times.

Other objects and advantages of the invention will become apparent from reading the following detailed description and upon reference to the drawings, in which:

FIG. 1 is a plan view of a cylinder-forming apparatus exemplifying the present invention illustrated in association with ancillary handling equipment;

FIG. 2 is a side elevation of the cylinder-forming apparatus and associated welding apparatus of FIG. I;

FIG. 3 is an end elevation of the cylinder-forming apparatus of FIG. 2;

FIGS. 4-8, inclusive, are partial schematic views of the forming mandrel in the cylinder-forming apparatus of FIG. 3, showing the apparatus in sequential operation; and

FIG. 9 is an enlarged fragmentary view partly in section illustrating the end elevation of the cylinder forming apparatus in the position substantially as shown in FIG. 3.

While the invention'is described in connection with a certain preferred apparatus and procedure, it will be understood that it is not confined to the exemplary embodiment and procedure described herein but on the contrary is applicable to all forming processes in which a blank of strip material is to be formed into a generally cylindrical shape with a resultant end gap which must be precisely positioned in a succeeding welding or other forming operation, without the need of special equipment to again find the gap in subsequent steps of fabrication.

BACKGROUND OF THE INVENTION Apparatus for forming strip material blanks into cylindrical shapes is commonly employed in manufacturing steel automobile wheels. The process of manufacturing such wheels requires that an initially flat blank of pre-cut strip material be formed into a cylinder and welded together to form a continuous ring which then serves as a blank for further forming processes. The ends of the strip are butted together and welded, leaving an upset portion or bead which must be trimmed and smoothed so that the resultant cylinder is substantially uniform about its circumference before it is transferred to other apparatus in which the drop center and flange portions of the rim are formed.

Previous forming operations in the manufacture of automobile wheels have used simple coiling apparatus consisting of three spaced rollers through which the strip material is drawn to produce a bend or curl of the required diameter. When a sufficient length of material has been so formed, it is cut off and the resultant formed blank is usually dropped into a hopper or chute for transferring to the subsequent welding operation.

In the welding operation the problems of the foregoing prior art process become apparent. The requirements of strength and uniformity in automobile wheels are quite strict and it has been found that only an electrical flash welder is capable of producing a welded joint of the necessary quality at mass production rates. The welder has welding jaws which grip the ends of the blank adjacent the gap and force them together while applying a heavy electrical current which serves to fuse the metal together. However, the performance of such a welder is acutely sensitive to the position of the gap to be welded. If the gap width of the blanks is not uniform, or if the gaps are not uniformly positioned from one blank to the next, the welding operation cannot be relied upon to produce welds of acceptable strength and soundness in high-volume automatic operation. Such welders are capable of production rates as high as 500 pieces per hour but the full utilization of this capacity has not been possible heretofore because of the need to individually locate and position the gap in each formed blank before insertion into the welder, often with a resultant bottleneck in production.

DESCRIPTION OF THE APPARATUS Turning to the drawings, there is shown in FIG. 1 a portion of a production line employing a forming machine 10 exemplifying the present invention. Pre-cut flat rectangular blanks 11 of sheet steel are carried in stacks by a conveyor 12 into an unstacking apparatus 13 having magnetic pickup units 14 which lift each individual blank 11 onto a transfer conveyor 15.

From the transfer conveyor 15 each blank 11 is carried into the forming machine 10, wherein it is formed by wrapping about a mandrel 16 as described hereinafter. From the mandrel 16 a transfer shuttle 17 carries the formed blank to an electric flash welding machine 18 having pairs of jaws 20 which grip the ends of the formed blank and force them together while passing a heavy electrical current through the joint to fuse the ends. When the welded joint has solidified, the welded blank is gripped by a gripper 21 on the arm 22 is enabled to grasp the welded blank, withdraw it from the welder l8, and swing it vertically overhead for transfer to a trimmer (not shown) and other subsequent apparatus as required for performing further steps in fabricating the automobile wheel.

The cylinder-forming machine exemplifying the present invention is shown in greater detail in FIGS. 2 and 3. The rotatable mandrel 16 is carried for rotation by heavy bearings in a head 25 mounted to a frame 26. A shaft 26 supporting the mandrel 16 protrudes through the rear of the head 25 and attaches to a gear 27 which is driven by a rotary actuator 28 through another gear 29. The rotary actuator 28 is of the rack and pinion type which is effective to reciprocate the gear 29 through of rotation. The ratio between the gears 27, 29 is 2:1, thereby reciprocating the gear 27 and the mandrel 16 over 360 of rotation, concluding in a predetermined end position.

The elements of the forming apparatus 10 which are effective to form the incoming blank 11 of strip material into a generally cylindrical shape are best seen in FIG. 3, and in FIGS. 4-8 wherein the sequence of forming operations is illustrated schematically. The incoming blank 11 is fed by the feeding means 15 to a first guide means consisting of a transverse roller 30 fixed to the frame 26 of the machine. The roller 30 is spaced from the periphery of the mandrel 16 so that a blank 11 resting on the upper surface of the roller 30 in a horizontal position is presented with its upper surface tangent to the mandrel 16.

The blank 11 is held in a clamp consisting of a pair of opposed jaws 31, 32 (FIG. 9) wherein it is first positioned against an abutment 33. Both the jaws 31, 32 and the abutment 33 are carried by the mandrel 16 and rotate with it through 360 under the power of the rotary actuator 28. The jaw 32 is fixed, being carried by a back-up support 35 which is cantilevered forward from the rear of the mandrel 16. The jaw 31 is movable in a radial direction by means of a hydraulic piston 36 carried within the mandrel 16 itself. Pressure fluid is introduced through a port 37 connected at the rear through a flexible hose (not shown) to a suitable control and supply source of pressure fluid. Because the mandrel 16 does not continuously rotate but only reciprocates through 360 from starting to end positions, no rotary connection is necessary. A return spring 38 causes the piston 36 and movable jaw 31 to retract when the pressure from the port 37 is relieved.

OPERATION In operation, a blank 11 is fed in over the guide roller 30 into the jaws 31, 32, where it is securely clamped by admitting pressure fluid to the hydraulic piston 36. It will be observed that the faces of the jaws 31, 32 are planar and substantially parallel to the plane of an incoming blank 11. The mandrel rotates (counterclockwise as seen in the figures) to draw blank 11 forward over the guide roller 30 and wrap it around the periphery of the mandrel 16 (FIG.

When the mandrel 16 has passed through approximately 270 of rotation the trailing end of the mandrel 16 passes over the guide roller 30 and is no longer constrained to follow the curvature of the mandrel 16. At this point a second forming roller 40 carried by a pivot frame 41 is urged against the mandrel 16 by a hydraulic cylinder 42 (FIG. 6) and the forming operation continues with the trailing end of the blank 11 being nearly completely wrapped against the periphery of the mandrel 16. At this point the mandrel 16 has completed 360 of rotation from its starting point (FIG. 4) to its end point (FIG. 7). The mandrel 16 has a flat surface on either side of the abutment 33, with one side consisting ofthe movable jaw 31 when in the clamped position against a blank 1 1. The forming process is then finished by the introduction of a flat-ended ram 43 into the space between the second guide roller 40 and the abutment 33 and against the flat surface of the mandrel 16. The ram 43 is carried by a pair of links 45, 46 and is urged against the mandrel 16 by a hydraulic cylinder 47.

With the blank 11 thus formed into substantially cylindrical shape, and with the end portions being slightly flattened where they define a gap separated by the abutment 33, pneumatically actuated grippers 50 are urged against the sides of the form blank 11 as the second guide roller 40 and ram 43 are withdrawn (FIG. 9). The formed blank 11 is thus securely held in the exact position which it occupied at the conclusion of the forming operation with the mandrel 16 in its predetermined end position, and the position of the gap between the ends of the blank 11 is therefore precisely determined.

The grippers 50 are actuated by pneumatic bellows 51 on opposite sides of a pick-up yoke 52 carried on a trolley 53. The trolley 53 runs on rails 54 above the machine overhanging the mandrel 16 and parallel to the axis of mandrel rotation. The trolley 53 is reciprocated by another rotary actuator 56 turning a crank arm 57 through 180 of movement, moving back and forth on the rails 54 to transfer the pick-up yoke 52 and the formed blank 11 carried by the grippers 50 into the jaws 20 of the welding machine 18. A link 58 connects the crank arm 57 to a pair of arms 60 which are connected through further links 61 to the trolley 53.

Removal of the formed blank 11 from the mandrel 16 is facilitated by providing a projecting finger 63 (FIG. 9) on each of the grippers 50 which, when the mandrel 16 is in its end position, travels in a corresponding axial groove 64 in the side of the mandrel. The fingers 63 are located at the rear of the grippers 50 so that the formed blank 11 is picked up from behind and carried outward in the grippers 50 on its way to the welding jaws 20.

Pursuant to the invention, the gaps in succeeding formed blanks are substantially identical in dimension and angular position due to the action of the various forming members including the mandrel l6, guide rollers 30, 40 and ram 42. The ends of each formed blank are precisely located with respect to the abutment 33 which serves as a spacer to assure a constant gap size from one formed blank to the next. While the details of the welding machine 18 are not shown, for the purposes of understanding the present invention it is only necessary to explain that the welding jaws 20 are disposed in two adjoining pairs to clamp the ends of the formed blank 1 l on each side of the gap. Once in the jaws 20 of the welding machine 18, the ends of the formed blank are forced together under a heavy electrical current which causes the metal within the gap to fuse under heat and pressure. This technique of flash or butt welding is well known and need not be described further.

From the welding machine 18, the swingover transfer arm 22 with its grippers 21 takes hold of the welded blank and transfers it over to further machines (not shown) which complete the forming process by trimming the upset bead from the weld and plannishing the remaining ridge by rolling the bead down flat.

With the pick-up yoke extended to carry the formed blank 1 l to the welding machine 18, the mandrel 16 is free to return to its starting position by reverse actuation of the rotary actuator 28. The second guide roller 40 and ram 42 are first retracted to allow the back-up frame of the mandrel 16 to clear as it returns to its starting position. At this point the hydraulic pressure behind the piston 36 is released, the movable jaw 31 returns to its open position, and the mandrel 16 is ready to receive the next succeeding blank while the pick-up yoke 52 and the grippers 50 (now retracted) are returned to the starting position for the next forming operation.

I claim:

1. Apparatus for forming blanks of strip material preparatory to welding the ends thereof with welding means, comprising in combination,

a mandrel mounted at one end for rotation, said mandrel carrying a radially outwardly extending locating abutment and clamping means on one side of the abutment for gripping a leading end of a blank positioned against the abutment and mandrel periphery,

power means for rotating the mandrel through a predetermined arc of rotation terminating with the mandrel and abutment at a predetermined end position,

first guide means spaced from the mandrel periphery and parallel to the axis of mandrel rotation, said first guide means being aligned with the mandrel and abutment in a starting position for positioning the leading end of an unforrned blank against the mandrel periphery, said abutment, and within the clamping means,

second guide means parallel to the axis of mandrel rotation and shiftable toward the mandrel periphery for forming a trailing end of the blank against the mandrel on the opposite side of the abutment from the clamping means when the blank has cleared the first guide means and the mandrel and abutment are at said predetermined end position,

ram means shiftable toward said mandrel on the opposite side of said abutment for pressing said trailing end of the blank against said mandrel periphery and said opposite side of said abutment and means for transferring said formed blank from the mandrel to said welding means with the blank in said predetermined position and welding said blank.

2. Apparatus as defined in claim 1 in which the first guide means includes a fixed guide roller, the second guide means includes a shiftable guide roller and power means for shifting the shiftable guide roller toward the mandrel, and the mandrel is rotatable through 360 from the starting position to the predetermined end position.

3. Apparatus as defined in claim 1 including gripping means for seizing a formed blank carried by the mandrel with the leading and trailing edges of the formed blank defining a gap having a predetermined position when the mandrel is in its predetermined end position, linear transfer means for transporting the gripping means to withdraw the formed blank axially from the mandrel, and welding means for receiving the formed blank from the transfer means with said gap in said predetermined position.

4. Apparatus as defined in claim 3 in which the welding means includes opposed gripping jaws for seizing the ends of a formed blank adjacent on each side of said gap, with said jaws being positioned linearly opposite the ends of a formed blank carried by the mandrel when the mandrel is in its predetermined end position.

5. The method of forming a blank of strip material preparatory to welding the ends thereof, comprising the steps of;

feeding the blank across a first guide means and into a clamp carried by a rotatable mandrel,

positioning the leading edge of the blank against a radially outwardly extending abutment adjacent to the clamp, contracting the clamp to grip the leading edge of the blank tangent to the periphery of the mandrel,

rotating the mandrel to partially form the blank against the periphery of the mandrel until the trailing edge portion of the blank is carried past the first guide means,

shifting a second guide means toward the mandrel periphery to engage the trailing edge portion of the blank,

further rotating the mandrel to a predetermined end position at which the trailing edge portion of the blank is formed against the periphery of the mandrel on the side of the abutment opposite the clamp,

shifting ram means to press the trailing edge end of the blank into engagement with the mandrel periphery adjacent the opposite side of said abutment,

removing the formed blank from the mandrel and directly shifting it to welding means with the blank in said predetermined end position and welding said blank.

6. The method defined in claim 5 in which the clamp and mandrel have flat planar surfaces on opposite sides of the abutment, and in which the step of shifting the ram means into forming engagement with the fiat surface of the mandrel on the side of the abutment opposite the clamp is characterized by said ram being fiat-ended.

7. The method defined in claim 5 in which removing the formed blank from the mandrel includes the steps of gripping the periphery of the formed blank,

releasing the mandrel clamping means,

withdrawing the formed blank from the mandrel in a linear direction with the gap defined by the leading and trailing edges of the blank being retained in a predetermined position, and transferring the formed blank to a welding means with the gap in said known predetermined position.

8. The method defined in claim 7 in which the transfer means carries the formed blank from the mandrel to the welding means in a linear path. r

9. Apparatus for forming blanks of strip material preparatory to welding the ends thereof with welding means, comprising in combination,

a mandrel mounted at one end for rotation, said mandrel carrying a radially extending locating abutment and clamping means on one side of the abutment for gripping a leading end of a blank positioned against the abutment and mandrel periphery,

power means for rotating the mandrel by a predetermined arc of rotation terminating with the mandrel and abutment at a predetermined end position,

first guide means spaced from the mandrel periphery and parallel to the axis of mandrel rotation, said first guide means being aligned with the mandrel and abutment in a starting position for positioning the leading end of an unformed blank within the clamping means,

second guide means parallel to the axis of mandrel rotation and shiftable toward the mandrel periphery for forming a trailing end of the blank against the mandrel on the opposite side of the abutment from the clamping means when the mandrel and abutment are at said predetermined end position,

said mandrel surface including flat coplanar surfaces on opposite sides of the abutment,

the clamping means including a pair of planar jaws,

power actuator means carried within the mandrel for contracting said jaws,

said second guide means further including a flat-ended ram shiftable toward the fiat mandrel surface adjacent the abutment on the opposite side from the clamping means when the mandrel is in its predetermined end position,

power means for actuating said ram, and

means for linearly transferring said formed blank from the mandrel to said welding means with the blanks in said predetermined position and welding said blank 

1. Apparatus for forming blanks of strip material preparatory to welding the ends thereof with welding means, comprising in combination, a mandrel mounted at one end for rotation, said mandrel carrying a radially outwardly extending locating abutment and clamping means on one side of the abutment for gripping a leading end of a blank positioned against the abutment and mandrel periphery, power means for rotating the mandrel through a predetermined arc of rotation terminating with the mandrel and abutment at a predetermined end position, first guide means spaced from the mandrel periphery and parallel to the axis of mandrel rotation, said first guide means being aligned with the mandrel and abutment in a starting position for positioning the leading end of an unformed blank against the mandrel periphery, said abutment, and witHin the clamping means, second guide means parallel to the axis of mandrel rotation and shiftable toward the mandrel periphery for forming a trailing end of the blank against the mandrel on the opposite side of the abutment from the clamping means when the blank has cleared the first guide means and the mandrel and abutment are at said predetermined end position, ram means shiftable toward said mandrel on the opposite side of said abutment for pressing said trailing end of the blank against said mandrel periphery and said opposite side of said abutment and means for transferring said formed blank from the mandrel to said welding means with the blank in said predetermined position and welding said blank.
 2. Apparatus as defined in claim 1 in which the first guide means includes a fixed guide roller, the second guide means includes a shiftable guide roller and power means for shifting the shiftable guide roller toward the mandrel, and the mandrel is rotatable through 360* from the starting position to the predetermined end position.
 3. Apparatus as defined in claim 1 including gripping means for seizing a formed blank carried by the mandrel with the leading and trailing edges of the formed blank defining a gap having a predetermined position when the mandrel is in its predetermined end position, linear transfer means for transporting the gripping means to withdraw the formed blank axially from the mandrel, and welding means for receiving the formed blank from the transfer means with said gap in said predetermined position.
 4. Apparatus as defined in claim 3 in which the welding means includes opposed gripping jaws for seizing the ends of a formed blank adjacent on each side of said gap, with said jaws being positioned linearly opposite the ends of a formed blank carried by the mandrel when the mandrel is in its predetermined end position.
 5. The method of forming a blank of strip material preparatory to welding the ends thereof, comprising the steps of; feeding the blank across a first guide means and into a clamp carried by a rotatable mandrel, positioning the leading edge of the blank against a radially outwardly extending abutment adjacent to the clamp, contracting the clamp to grip the leading edge of the blank tangent to the periphery of the mandrel, rotating the mandrel to partially form the blank against the periphery of the mandrel until the trailing edge portion of the blank is carried past the first guide means, shifting a second guide means toward the mandrel periphery to engage the trailing edge portion of the blank, further rotating the mandrel to a predetermined end position at which the trailing edge portion of the blank is formed against the periphery of the mandrel on the side of the abutment opposite the clamp, shifting ram means to press the trailing edge end of the blank into engagement with the mandrel periphery adjacent the opposite side of said abutment, removing the formed blank from the mandrel and directly shifting it to welding means with the blank in said predetermined end position and welding said blank.
 6. The method defined in claim 5 in which the clamp and mandrel have flat planar surfaces on opposite sides of the abutment, and in which the step of shifting the ram means into forming engagement with the flat surface of the mandrel on the side of the abutment opposite the clamp is characterized by said ram being flat-ended.
 7. The method defined in claim 5 in which removing the formed blank from the mandrel includes the steps of gripping the periphery of the formed blank, releasing the mandrel clamping means, withdrawing the formed blank from the mandrel in a linear direction with the gap defined by the leading and trailing edges of the blank being retained in a predetermined position, and transferring the formed blank to a welding means with the gap in said known predetermined position.
 8. The method defined in claim 7 in which the transfer means carries the formed blank from the mandrel to the welding means in a linear path.
 9. Apparatus for forming blanks of strip material preparatory to welding the ends thereof with welding means, comprising in combination, a mandrel mounted at one end for rotation, said mandrel carrying a radially extending locating abutment and clamping means on one side of the abutment for gripping a leading end of a blank positioned against the abutment and mandrel periphery, power means for rotating the mandrel by a predetermined arc of rotation terminating with the mandrel and abutment at a predetermined end position, first guide means spaced from the mandrel periphery and parallel to the axis of mandrel rotation, said first guide means being aligned with the mandrel and abutment in a starting position for positioning the leading end of an unformed blank within the clamping means, second guide means parallel to the axis of mandrel rotation and shiftable toward the mandrel periphery for forming a trailing end of the blank against the mandrel on the opposite side of the abutment from the clamping means when the mandrel and abutment are at said predetermined end position, said mandrel surface including flat coplanar surfaces on opposite sides of the abutment, the clamping means including a pair of planar jaws, power actuator means carried within the mandrel for contracting said jaws, said second guide means further including a flat-ended ram shiftable toward the flat mandrel surface adjacent the abutment on the opposite side from the clamping means when the mandrel is in its predetermined end position, power means for actuating said ram, and means for linearly transferring said formed blank from the mandrel to said welding means with the blanks in said predetermined position and welding said blank. 